1. Field of the Invention
Chucks for use with power tools to interchangeably accept and hold tools, such as wood or other cutting tools, especially router bits, of simple, lightweight design, improving manufacturing and assembly techniques, but providing significant tool holding torque, are disclosed.
2. Discussion of the Related Art
Power tools to drive cutting, boring, and other tool elements are well known.
U.S. Pat. No. 5,096,212 to Joseph P. Walsh (the entire disclosure of which is herein incorporated by reference in its entirety) provided a significant advance in chucks suitable for use in coupling a power driven shaft to such tools, especially router bits. Such a chuck (illustrated in FIG. 1 (PRIOR ART)) comprised a chuck body 11, provided with an aperture 114 into which a collet 115 can be inserted.
The other end of aperture 114 was provided with means, such as internal threads 120 (FIG. 2 (PRIOR ART)) for attachment to an electrically, pneumatically, hydraulically or other driven shaft. A collet 115 is insertable into aperture 114 and the shank 100 of cutting element 101 were secured in aperture 114 through the provision of a clamping mechanism extending through a bore 116 extending through aperture 114. The clamping mechanism comprised two clamping elements 108, 109 pulled together by means of a screw 110. At least clamping element 108 was threaded 90 to accept the threads 94 of screw 110 such that upon tightening the threads, screw head 96 clamped elements 108, 109 about collet 115 (or alternatively directly on the shaft 100 of cutting element 101) to securely couple the cutting element 101 and the power driven shaft of the power tool.
Although a great advance over the prior art chucks, the Walsh invention had several drawbacks.
The provision of bore 116 to accommodate two clamping elements extending through aperture 114 made the size of the chuck body relatively large and bulky to accommodate the clamping elements. Still further, clamp elements 108, 109 had to have alignment elements, such as keys and keyways 108', 109' to retain them in a desired orientation with regard to collet 115, or shank 100, of cutting element 101.
The large size of the chuck exacerbated balancing as such chucks were used in routers known to revolve at speeds above 20,000 rpm (revolutions per minute).
Runout of the cutting element 101 became a problem as it was impossible to use threads 120 to simultaneously couple the chuck body 112 to the power driven shaft (not shown) while attempting to also align the respective centerline of the shank 100 and power driven shaft (not shown).
Another attempt at providing a chuck for a cutting tool is found in U.S. Pat. No. 5,348,319. In the device of that patent, a cam was provided which was pivotably mounted and activated by a set screw. However, the lever end of the cam, in conjunction with the set screw, could not generate sufficiently high holding power to withstand the forces tending to dislodge a cutting tool, especially a cutting tool rotating at high speed, such as in a router. To increase the length of the lever end of the cam would require enlarging the size of the chuck to accommodate the increased length, further tending to create a large and bulky mass, which, when subjected to high rotational speeds, would introduce additional problems which negates the proposed utility of the device as a chuck.
None of the attempts known to the inventor have been able to improve the requirements of a chuck for holding cutting, boring or other tools, and, especially, no one skilled in the art has provided an easy to use router chuck having acceptable torque for holding a cutting element without slippage while permitting ease of construction of the chuck.